UNIVERSITY OF CALIFORNIA AGRICULTURAL EXPERIMENT STATION
«*#«■• w~m *%..- m~~.~.... —...._ BENJ. IDE WHEELER, President
COLLEGE OF AGRICULTURE
THOMAS FORSVTH HUNT, EAN AN D D I R ECTOR
BERKELEY H. E. VAN NORMAN, Vice-Director and DrAN
University Farm School
CIRCULAR No. 20:3
PEAT AS A MANURE SUBSTITUTE
By JOHN S. BURD
(Chemist in Charge of Fertilizer Control, Professor of Agricultural Chemistry,
University of California.)
The present tendency of soil and fertilizer investigations is to
emphasize the importance of materials of organic origin as soil amend-
ments. The virtue of such substances lies partially in the fact that
they invariably contain small proportions of necessary chemical
elements (so-called "plant foods"), but considerable importance is
also attached to certain characteristic properties of the organic (non-
mineral) components. Among these may be mentioned their great
water-holding power, capacity for serving as nutrient media for cer-
tain beneficial organisms (bacteria, molds, etc.), and indirect action
on the mineral particles of the soil or the soil solution.
Soils of the humid region normally contain several per cent of
organic matter. The amount depends upon many factors, but the
finer soils (clays and loams) usually carry more than do* the coarse
soils (sands). In California and other arid sections the high tempera-
ture and low and variable moisture content have the effect both of
preventing the accumulation of organic matter and of causing it to
disappear rapidty from cultivated soils of all kinds. The average
organic matter content of arid soils seems to be less than 1 per cent,
i.e., from one-half to one-quarter that of similar soils of the humid
region. Additions of even large amounts of decaying organic matter
to arid soils will only serve to raise the amount of that material tempo-
rarily, because the conditions are unfavorable to its accumulation.
Indeed, if organic matter is to be effective the material must decay
and thus disappear from the soil.
To maintain the organic matter in arid soils, therefore, requires
the constant addition of the manure of domestic animals, green
manures or cover crops, or of straw or hay which has been rendered
unfit for animal feed. Any kind of vegetative tissue which is capable
of decay in the soil may be used but it is v exceedingly doubtful if
materials from other sources are worth any more than the cost of
application. This means that the farmer should use such waste
materials from his own place but that their argicultural value is too
problematical to warrant their purchase from others.
EVALUATION OF MANURES
The well known deficiencies of arid soils with reference to organic
matter have caused our farmers to search everywhere for such
material. The value of manure as a soil amendment is unquestioned,
but different lots may vary in effectiveness and a determination of
their relative values presents an exceedingly complex and technical
problem. The whole question of soil fertility is involved and farmers
may not hope in the present state of our knowledge to obtain exact
statements as to the commercial value of a given lot of manure. The
following principles are suggested as the proper basis for purchasing
1. Whenever possible buy on a basis of the organic content of the
2. If several lots of manure are procurable at different prices, the
cheapest "buy" may be determined by dividing the price per ton by
the percentage of organic matter (i.e., the price per unit of organic
3. The nitrogen content of the manure may be ignored because
the nitrogen will vary with the organic content within sufficiently
narrow limits for this purpose.
4. Ignore the phosphoric acid and potash of the manure because
the former is usually insignificant and the latter is relatively unim-
portant as a fertilizer on California soils.
5. Considerable variation in the amount of added straw in manure
is permissible as dry straw contains more organic matter than fresh
6. The amount of water and sand or stones is not material if the
manure is purchased on the unit basis for organic matter, except that
it increases the transportation charges.
7. A limited amount of sawdust or shavings in manure is to be
regarded as legitimate, but manures containing excessive amounts
should be rejected.
8. Manures containing sticks or visible woody material other than
sawdust or shavings should be rejected even if offered at a lower price.
We are well aware that there are certain very practical obstacles
to the purchase of manures on the unit basis of organic matter. A
strict regard for the other principles outlined will, however, if com-
bined with a little common sense and experience enable anyone to buy
as effectively as the market conditions permit. Chemical analyses
for nitrogen, phosphoric acid and potash are of minor value and
constitute an unnecessary expense or actual waste of time on the part
of the Experiment Station. Such analyses will ordinarily be refused.
HUMUS VERSUS TOTAL ORGANIC MATTER
A great deal of loose talk is heard with reference to humus in the
soil. If by humus is meant organic matter of vegetable origin capable
of decay under the conditions existing in normal soils, the use of the
term is perhaps legitimate. The term humus, however, is ordinarily
applied to that portion of any material of organic origin which is
soluble in dilute alkalies. The use of the term in this sense was quite
common a few years ago. It is, however, now generally recognized
that the humus determination in soils and soil amendments is abso-
lutely worthless as an indicator of fertility or fertilizing value. The
reason for this is that solubility in alkali affords no guaranty that
any portion of the material so dissolved will decay in the soil; fur-
thermore organic matter which is not soluble in alkalies may decay
and be a valuable addition to the soil.
The well known defects of the humus determination and the
conviction that it has no meaning in terms of soil fertility lead us
to urge the abandonment of the use of this term. Farmers should
therefore purchase manures or manure substitutes without regard to
humus content, but with strict regard to the probable total of organic
CONCENTRATED MANURE, HUMUS AND PEAT
The term manure, as used in this country, is confined to the excre-
ments of domestic animals more or less mixed with bedding material.
Concentrated manure should only be used with reference to manure
which has been dried. The use of the term manure or concentrated
manure when applied to substitutes of other origin is fraudulent.
For the reasons indicated heretofore any representation put forth
in attempts to sell any substance which includes a statement that
the material contains a definite percentage of humus is either fraud-
ulent in its intent or based on ignorance of the present status of the
Deposits of partially decayed remains of plants owing their
preservation to submergence in water are technically known as peat.
It is not legitimate to refer to such substances as humus or concen-
trated manure, no matter how they have been treated. Their uses
and limitations as soil amendments are set forth hereafter.
While normal soils contain only a few per cent of organic matter,
certain soils contain very large proportions of this material and the
mineral constituents are relatively low. This class comprises muck
and peat soils, the latter of which may contain in the dry state 80
per cent or more of organic matter. Peat soils owe their origin to
the fact that successive generations of native plants growing in stand-
ing water become submerged on completing their growth and the
processes of decay characteristic of normal soils do not take place.
The excess of water prevents the access of air and acts as a preserva-
tive. In this manner successive layers of plant residues are laid down
year after year and the deposits may accumulate to a considerable
depth. In the peat so derived the structure of the plants to which
they owe their origin is still intact and gives testimony as to the
incompleteness of their decomposition. Peat soils may occur in any
place where native growth is prolific and where such growth becomes
submerged. They occur extensively in glaciated regions in the glacial
ponds or lakes and also in marshes and low-lying lands elsewhere. In
the "delta" region of the San Joaquin and Sacramento rivers in
California large areas of peat lands are under cultivation ; more limited
areas occur in other parts of the state.
As stated above large areas of peat lands are under cutlivation
and when properly drained and free from disease may produce excel-
lent crops of barley, potatoes, etc. These soils are usually highly acid,
even in the well-drained and aerated surface soil; at the same time
they frequently contain considerable quantities of soluble salts. In
common parlance such soils would be said to be both acid and
"alkaline." There is this difference between the real acidity and the
so-called "alkalinity" that the acidity does not seem to be sufficient
to prevent the growth of good crops but that the soluble salts tend
to increase under cultivation and cause a falling off in yield after
PEAT AS A SOIL AMENDMENT
Owing to the dearth and high price of farmyard manure it is not
surprising that the practically inexhaustible supply of peat with its
high organic content has been suggested as a possible substitute for
this valuable amendment.
A discussion as to the value of any material used to improve the
producing capacity of a soil must be based in part on the amount of
the important constituents and in part upon their so-called avail-
ability. It is evident that very small percentages of the important
constituents in a fertilizer or amendment cannot have any material
effect in modifying the composition of a soil, no matter how "avail-
able ' ' they may be ; on the other hand, large percentages will be
equally ineffective if of low availability.
The two constituents which peat might be expected to add to a
soil when used as a fertilizer or amendment are organic matter and
nitrogen. The total organic matter and total nitrogen of fresh peat
approximate more nearly in amount to that of farmyard manure than
to any other substance commonly applied to soils. We may therefore
logically compare peat with manure, a method which has the addi-
tional advantage of using as a standard a material of well known
Analyses of Peat
(Expressed as percentages of the fresh material)
Subsurface Subsurface Subsurface
Surface (drained) (wet) (wet)
12 3 4
Water 66.23 68.93 64.74 78.11
Organic matter 18.74 24.37 22.28 13.84
Mineral matter (ash) 15.03 6.70 12.98 8.05
Total 100.00 100.00 100.00 100.00
Plant Food Content of Peat
(Three different samples)
Per cent Per cent Per cent
Nitrogen 0.61 0.86 0.49
Phosphoric acid 0.16 0.17 0.12
Potash 0.19 0.12 0.06
Farmyard manures are of variable composition, depending on the
kind of animal, age, method of feeding, amount of straw, etc. We
may take as an average for fresh manure with some straw about 20
per cent of organic matter, 0.50 per cent nitrogen, 0.25 per cent phos-
phoric acid and 0.60 per cent potash. The peat analyses here given
show that this material contains roughly about the same total of
organic matter (varying from considerably less to slightly more) than
manure; that the nitrogen content of both substances is about the
same (many samples of manure contain more nitrogen than many
peats) ; and finally, that the peats all contain much less phosphoric
acid and potash than the average sample of manure. It is clear that
even if it were true that the organic matter of fresh peat decomposes
with the same facility as that of manure and if the availability of
the so-called plant foods in peats is equal to that of manure, the peat
could not possibly be considered as of equal value to the average fresh
DECOMPOSABILITY OF PEAT
A peat soil, even when drained and aerated, or a pile of the same
material, will maintain its initial appearance almost indefinitely, in
marked contrast to the manure pile, in which fundamental changes
may be observed from time to time. No one who has made such
observations can fail to be impressed by the difference between the
two substances and the obvious inertness of the former. It is evident
that such inert material as peat is incapable of the rapid decay usually
associated with "available" materials like manure.
Much work has been done by several investigators on the nitro-
genous constituents of peat. The general conclusion with reference
thereto may be epitomized by the following quotation. 1 "Practically
all the nitrogen in the peats is of organic nature. Through weathering
the organic nitrogenous bodies present in the brown peat change quite
slowly. ' '
We have observed in this laboratory that peat from California
sources is similar to that from other sources referred to above in that
its nitrogen consists almost entirely of organic nitrogen and not of
the highly available nitrate and ammonia salts. The Citrus Experi-
ment Station at Riverside has made similar observations and, in
addition, nitrification studies which unquestionably demonstrate the
low availability of peat nitrogen. The conclusions reached in these
experiments are indicated from the following excerpt from a report
of Dr. W. P. Kelley, Professor of Agricultural Chemistry, Citrus
Experiment Station, Riverside, California.
. . . After the above experiments had stood for a year a study was also made
of the effects that had been produced on the solubility of the various plant foods
present. The results showed that in neither case had any appreciable effect been
produced by the peat. The manure and alfalfa hay, on the other hand, had
notably increased the solubility of the various plant food elements present.
From the preceding results, it is evident that the peat used in these experiments
is an extremely inert substance, and that it is of such nature as to be practically
unaffected by the action of soil bacteria. The fact that the peat produced no
effect either on nitrification or dentrification, on the one hand, or on the solubility
i Tech. Bull. No. 4, Michigan Agr. College, Nov., 1909, p. 28, Organic Nitro-
genous Compounds in Peat Soils.
of the plant food constituents contained in the soil, on the other, is especially
strong evidence in support of this view. It would appear reasonable to conclude,
therefore, that the chemical and biological effects produced by this material, at
least for the first year after it has been applied, will be negligible, and since the
plant foods contained in the peat itself are largely unavailable, the effects that
will be produced on crops under field conditions, will probably not be great.
In addition to the above experiments, I have frequently observed the conditions
in certain citrus groves near Eiverside where peat has been in use for some time,
but as yet no apparent effects have been produced on the growth or well-being
of the trees. The lumps of peat can still be seen in the soil, and careful exam-
ination shows that it has not undergone any apparent change. Ordinarily, stable
manure when applied in this section becomes completely decomposed in much less
time than has elapsed since the application of peat in the groves referred to.
In view of the well known experience with peat in other parts of the world,
and the information derived from the above studies on this material, it seems
safe to conclude that the farmer in California is not justified in placing more than
a nominal fertilizing value on this material.
(Signed) W. P. Kelley.
In the laboratory of Agricultural Chemistry at Berkeley we have
demonstrated that virgin peat soils gave a three-fold crop when
fertilized with phosphate fertilizers, indicating very clearly that the
phosphate in fresh peat is likely to be highly unavailable. We have
made no studies as to the availability of potash in peat, but as stated
above, the total potash is so small as to be negligible. Peat contains
from a third to a tenth or less potash than the normal California soil
so that its addition would actually decrease the percentage of total
potash in soils on which it is used.
Peat like any other watery material can be concentrated by the
simple process of evaporating the water. The effect of this is to
increase the amount of each non-volatile constituent in proportion to
the loss of water. The advantage to be derived from this practice is
that the resulting material weighs only about a third as much as the
original peat and contains about three times as much of each con-
stituent (other than water) in a ton of dried material.
If peat has any fertilizing value the drying is justifiable in that
it saves about two-thirds of the transportation charges if the drying
is thorough. Such substances tend to absorb considerable quantities
of moisture from the air, however, so that the proportionate increased
concentration estimated above represents a maximum figure for peat
of average composition.
ILL EFFECTS OF DRYING
Drying or desiccation of vegetative material has been observed to
decrease its capacity for rapid nitrification, even when subsequently
moistened and added to soils. 2 A portion at least of the benefit of
drying peat may be lost by a lowering of the nitrifiability of the
DRIED PEAT VERSUS FARMYARD MANURE
The statement is frequently made that dried peat is more con-
centrated than fresh farmyard manure. This is true but it is quite
possible to dry farmyard manure and thus obtain a much more
concentrated product than dried peat. The reason for this is that
while fresh peat and fresh farmyard manure contain about the same
percentages of organic matter, the remaining material in manure is
largely water, while peat normally contains much more of valueless
ash or mineral ingredients which reduce the percentage of organic
matter in the dried product.
The claim is frequently made that peat may be advantageously
inoculated with various organisms, thereby increasing the availability
of its nitrogen content or enhancing the nitrogen-fixing power of soils
to which it is applied. A very clear exposition of the prevailing
opinion of scientific men with reference to the possibilities of inoculat-
ing peat may be obtained from the following letter from Dr. Chas.
B. Lipman, Professor of Soil Chemistry and Bacteriology, University
. . . The only extensive studies which have been made on the inoculation of
peat are those which were carried out in England by Bottomley and his associates
at the University of London, and those carried out by Voelcker at the Woburn
Experiment Station, by Eussell and his associates, at the Eothamsted Experiment
Station, and by Chittenden, both of which latter were intended to check the claims
of Bottomley. Mr. Bottomley 's claims were that peat is very much improved for
purposes of soil amendment by its inoculation with bacteria closely similar to
many of the so-called ammonifying or ammonia-producing- bacteria in the soil.
The idea involved is that the very inert organic nitrogenous compounds contained
in the peat are rendered soluble and easily hydrolizable through the action of the
micro-organisms. It has been further claimed by Bottomley that some of the
dissolved organic compounds thus produced may serve after the sterilization of
the peat as markedly efficient sources of energy for micro-organisms which have
2 Stewart, G. E., Availability of the Nitrogen in Pacific Coast Kelps, Journal
of Agricultural Eesearch, vol. IV, no. 1, April, 1915.
the power of fixing nitrogen from the air, and which have been introduced into
such sterilized peat. The material thus prepared is commercially known as
1 ' Humogen ' ' or bacterized peat. Bottomley and some of his commercial sup-
porters have carried out experiments and shown photographs of the plants involved,
which are calculated to substantiate their extravagant claims for the improvement
of the peat through inoculation.
The other English experiments which are referred to above, however, have
given little or no support to the claims made by Bottomley. Chittenden and
Russell, in particular, have gone on record as saying that, in their experiments,
the plants grown on soils treated with the bacterized peat do not seem to have
been affected beneficially any more than plants grown on similar soils not treated
with that substance. In view of the fact that such careful experimenters, prob-
ably among the most conservative in the field of agricultural science, have made
these statements renders it necessary for any one commenting on the subject in
question to decide that the public will be unjustly and unscientifically advised
if it is not warned that many more experiments by careful students of the sub-
ject are necessary before the exact facts in the case can be ascertained. In view,
therefore, of this situation, coupled with the traditional information which we
have always had relative to the inert nature of peat and its ineffectiveness when
applied to soils, make it necessary for me to advise against the acceptance by the
public of any statements made on the superior nature of inoculated as against
uninoculated peat, as well as on its value as a source of nitrogen and even of
organic matter to soils.
(Signed) Chas. B. Lipman.
SAND OR SILT IN PEAT
When peat beds are subjected to the influence of rising or falling-
water they are always more or less contaminated with mineral par-
ticles of sand, silt, or clay. The effect of this is to render the resulting
material still less valuable as a soil amendment, the mineral particles
constituting a worthless filler.
1. The substances commonly included in the term organic matter
and derived from plant or vegetative tissues have a recognized value
as soil amendments apart from their plant food contents.
2. Organic matter is contained in manures of all kinds, in straw,
hay, etc., and in peat.
3. The commercial value of substances of the same kind, such as
manures, should be based upon their percentages of organic matter.
4. Fresh peat contains about the same amount of organic matter
as the average fresh manure.
5. Dried peat will normally contain less organic matter than
manure of the same degree of dryness.
6. Peat, unlike farmyard manure, does not decay rapidly in the
soil, nor is it readily nitrified ; it cannot, therefore, be regarded as an
' ' available ' ' material.
7. We regard the inoculation of peat as a useless procedure and
an unnecessary expense to the farmer.
8. Peat frequently contains considerable sand or silt, making it
still less valuable agriculturally.
9. Any plant substance which has undergone partial decay in
water is to be regarded as peat.
10. In the absence of more favorable results than those heretofore
obtained in experiments with peat, the use of this material is not
11. Farmers are expressly advised that the plant food constituents
of peat are not to be regarded as having the same commercial value
as those of high grade fertilizers nor is peat commercially or agri-
culturally as valuable as farmyard manure.
STATION PUBLICATIONS AVAILABLE FOR FREE DISTRIBUTION
Humus in California Soils.
Utilization of the Nitrogen and Organic
Matter in Septic and Imhoff Tank
Deterioration of Lumber.
Irrigation and Soil Conditions in the
Sierra Nevada Foothills, California.
The Citricola Scale.
New Dosage Tables.
Melaxuma of the Walnut, "Juglans
Citrus Diseases of Florida and Cuba
Compared with Those of California.
Size Grades for Ripe Olives.
The Calibration of the Leakage Meter.
Cottony Rot of Lemons in California.
A Spotting of Citrus Fruits Due to the
Action of Oil Liberated from the Rind.
Experiments with Stocks for Citrus.
Growing and Grafting Olive Seedlings.
A Comparison of Annual Cropping, Bi-
ennial Cropping, and Green Manures
on the Yield of Wheat.
Feeding Dairy Calves in California.
Preliminary Report on Kearney Vine-
yard Experimental Drain.
Correspondence Courses in Agriculture.
Increasing the Duty of Water.
Grafting Vinifera Vineyards.
Alfalfa Silage for Fattening Steers. 166.
Spraying for the Grape Leaf Hopper. 167.
House Fumigation. 168.
The Control of Citrus Insects. 169.
Spraying for Control of Walnut Aphis. 170.
Countv Farm Adviser.
Official Tests of Dairy Cows. 172.
Melilotus Indica. 174.
Wood Decay in Orchard Trees. 175.
The Silo in" California Agriculture.
The Generation of Hydrocyanic Acid 176.
• Gas in Fumigation by Portable Ma-
The Practical Application of Improved 179.
Methods of Fermentation in Califor-
nia Wineries during 1913 and 1914. 181.
Practical and Inexpensive Poultry Ap-
Control of Grasshoppers in Imperial
Oidium or Powderv Mildew of the Vine. 184.
Tomato Growing in California. 186.
Round Worms in Poultry. 188.
Feeding and Management of Hogs. 189.
Some Observations on the Bulk Hand- 191.
ling of Grain in California. 192.
Announcement of the California State 193.
Dairv Cow Competition, 1916-18. 196.
Irrigation Practice in Growing Small 197.
Fruits in California.
Bovine Tuberculosis. 198.
How to Operate an Incubator. 200.
Control of the Pear Scab.
Home and Farm Canning. 201.
Lettuce Growinsr in California. 202.
Potatoes in California.
White Diarrhoea and Cocoidiosis of
The Common Honey Bee as an Agent
in Prune Pollination.
The Cultivation of Belladonna in Cali-
Irrigation of Rice in California.
Irrigation of Alfalfa in the Sacramento
Control of the Pocket Gophers in Cali-
Trials with California Silage Crops for
The Olive Insects of California.
Irrigation of Alfalfa in Imperial Valley.
Potash from Tule and the Fertilizer
Value of Certain Marsh Plants.
The June Drop of Washington Navel
The Common Honey Bee as an Agent
in Prune Pollination. (2nd report.)
Green Manure Crops in Southern Cali-
Sweet Sorghums for Forage.
Bean Culture in California.
Fire Protection for Grain Fields.
Topping and Pinching Vines.
Small Fruit Culture in California.
Fundamentals of Sugar Beets under
The County Farm Bureau.
Feeding Stuffs of Minor Importance.
Spraying for the Control of Wild Morn-
ing-Glory within the Fog Belt.
The 1918 Grain Crop.
Fertilizing California Soils for the
Farm Drainage Methods.
Progress Report on the Marketing and
Distribution of Milk.
Hog Cholera Prevention and the
Factors of Importance in Producing
Milk of Low Bacterial Count.
Control of the California Ground
Extending the Area of Irrigated Wheat
in California for 1918.
Infectious Abortion in Cows.
A Flock of Sheen on the Farm.
Poultry on the Farm.
Utilizing the Sorghums.
Winter Forage Crops.
Pruning the Seedless Grapes.
Cotton in the San Joaquin Valley.
A Study of Farm Labor in California.
Dairy Calves for Veal.
Suggestions for Increasing Egg Pro-
duction in a Time of High-Feed Prices.
Syrup from Sweet Sorehum.
Growing the Fall or Second Crop of
Potatoes in Califoi-nia.
Helpful Hints to Hog Raisers.
County Organization for Rural Fire